*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html, body {
  height: 100%;
}

body {
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: #f3f4f6;
  color: #111827;
  display: flex;
  justify-content: center;
  align-items: center;
}

.app {
  width: 100%;
  max-width: 420px;
  background: #ffffff;
  border-radius: 20px;
  box-shadow: 0 12px 30px rgba(0, 0, 0, 0.08);
  padding: 24px 20px 18px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.app-header {
  text-align: center;
}

.app-header h1 {
  font-size: 1.4rem;
  font-weight: 600;
}

.app-main {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
}

.counter-display {
  font-size: 4rem;
  font-weight: 700;
  padding: 16px 24px;
  border-radius: 16px;
  background: #f9fafb;
  min-width: 160px;
  text-align: center;
}

.counter-buttons {
  display: flex;
  gap: 12px;
}

.btn {
  border: none;
  border-radius: 999px;
  padding: 12px 22px;
  font-size: 1.3rem;
  font-weight: 600;
  cursor: pointer;
  outline: none;
  transition: transform 0.1s ease, box-shadow 0.1s ease, opacity 0.1s ease;
}

.btn-primary {
  background: #2563eb;
  color: #ffffff;
  box-shadow: 0 6px 14px rgba(37, 99, 235, 0.35);
}

.btn-secondary {
  background: #e5e7eb;
  color: #111827;
  box-shadow: 0 4px 10px rgba(0,0,0,0.08);
}

.btn-reset {
  margin-top: 4px;
  width: 100%;
  background: #f97316;
  color: #ffffff;
  font-size: 0.95rem;
  padding: 10px 18px;
  box-shadow: 0 6px 14px rgba(249, 115, 22, 0.35);
}

.btn:active {
  transform: translateY(1px) scale(0.98);
  box-shadow: none;
  opacity: 0.9;
}

.app-footer {
  text-align: center;
  font-size: 0.8rem;
  color: #6b7280;
}